binder: Add getCertificate / addTrustedPeerCerticate.

getCertificate returns the self-signed certificate
on this context.

addTrustedPeerCertificate adds a peer certificate
as trusted by this context.

Test: binderRpcTest
Bug: 195166979
Change-Id: I0e4fadd8e3391dc39f551e4b80e9411b16b696ab
diff --git a/libs/binder/RpcTransportTls.cpp b/libs/binder/RpcTransportTls.cpp
index 82c558b..e6cb04e 100644
--- a/libs/binder/RpcTransportTls.cpp
+++ b/libs/binder/RpcTransportTls.cpp
@@ -456,12 +456,24 @@
     static std::unique_ptr<RpcTransportCtxTls> create();
     std::unique_ptr<RpcTransport> newTransport(android::base::unique_fd fd,
                                                FdTrigger* fdTrigger) const override;
+    std::string getCertificate(CertificateFormat) const override;
+    status_t addTrustedPeerCertificate(CertificateFormat, std::string_view cert) override;
 
 protected:
     virtual void preHandshake(Ssl* ssl) const = 0;
     bssl::UniquePtr<SSL_CTX> mCtx;
 };
 
+std::string RpcTransportCtxTls::getCertificate(CertificateFormat) const {
+    // TODO(b/195166979): return certificate here
+    return {};
+}
+
+status_t RpcTransportCtxTls::addTrustedPeerCertificate(CertificateFormat, std::string_view) {
+    // TODO(b/195166979): set certificate here
+    return OK;
+}
+
 // Common implementation for creating server and client contexts. The child class, |Impl|, is
 // provided as a template argument so that this function can initialize an |Impl| object.
 template <typename Impl, typename>